The initial adhesive contacts between leukocytes and vascular endothelial cells are mediated by cell adhesion molecules called selectins. The selectin family of adhesion molecules mediate leukocyte tethering and rolling interactions on endothelial cells. Their expression on either the leukocyte (L-selectin) or endothelium (P- and E-selectin) helps the leukocyte “slow down” enabling cells in flow to respond to chemokine/cytokine signals, firmly attach and migrate through the endothelial lining into a tissue site. This primary intravascular braking mechanism is controlled by the Ca++ dependent binding activity of the selectins directed against their respective ligands, which are comprised of carbohydrate determinants displayed on cell surface proteins or lipids expressed on leukocytes and/or endothelial cells. The cooperative involvement of all selectins and selectin ligands is critical for rapid and efficient recruitment of leukocytes at sites of inflammation. These molecular interactions are also necessary for the maintenance of steady state host immunity and tissue-specific homing as illustrated in lymphocyte homing to peripheral lymph nodes (L-selectin-mediated), trafficking of human memory T-cells to skin (E selectin-mediated), and human progenitor cell (HPC) entry into the bone marrow (BM) (E-selectin-mediated). The latter two paradigms represent physiologically relevant processes that are dependent, at least in part, on the cell adhesive interactions between vascular E-selectin, which is constitutively expressed on post-capillary venules in the skin and BM, and its leukocyte E-selectin ligands. The cell-specific expression of leukocyte E-selectin ligands is, therefore, an important feature in developing therapeutic strategies to selectively control the extent of leukocyte infiltration associated with the progression of skin or bone-marrow-related diseases.
Analogs of the naturally occurring cell surface carbohydrate N-acetylglucosamine (GlcNAc) have been synthesized that are fully-acetylated and possess an isosteric substitution of a fluorine for a hydroxyl group at the carbon 3- and 4-positions, 2-acetamido-2-deoxy-1,4,6-tri-O-acetyl-3-deoxy-3-fluoro-D-glucopyranose (3-F-GlcNAc) and 2-acetamido-2-deoxy-1,3,6-tri-O-acetyl-4-deoxy-4-fluoro-D-glucopyranose (4-F-GlcNAc) (Bernacki, R. J. et al. (1977) J. Supra. Stru., 7:235–250; Sharma, M. and W. Korvtnyk (1980) Carbohyd. Res., 79:39–51; Sharma, M. et al. (1990). Carbohyd. Res., 198:205–22):
This structural modification has been postulated to cause the termination of poly-N-acetyllactosamine chain elongation or to inhibit the enzymatic processes of glycoconjugate metabolism involved in oligosaccharide biosynthesis (Bernacki, R. J. et al. (1977) J. Supra. Stru., 7:235–250). There is strong evidence that these compounds enter the cell by passive diffusion, rapidly de-O-acetylate and form UDP-fluorinated-N-acetylglucosamine, and incorporate into tumor cellular glycoproteins (Bernacki, R. J. et al. (1977) J. Supra. Stru., 7:235–250). Studies evaluating the effects of the fluorinated N-acetylglucosamine analogs 3-F-GlcNAc and 4-F-GlcNAc on human colon and ovarian cancer cell surface carbohydrate structure and glycoprotein function show that 3- or 4-F-GlcNAc treatment results in the selective termination of poly-N-acetyllactosamine chain formation and modulates the structure and function of tumor-associated glycoproteins (Woynarowska, B. et al. (1996) Glycoconjugate J., 13(4):663–674; Woynarowska, B. et al. (1994) J. Biol. Chem., 269(36):22797–22803). More specifically, treatment of human colon HT-29 cancer cells with 4-F-GlcNAc results in the inhibition of radiolabeled glucosamine, fucose and galactose incorporation into cell surface glycoproteins leading to quantitative reductions and qualitative structural changes in tumor-associated antigens: carcinoembryonic antigen (CEA), lysosomal-associated membrane proteins-I and 2 (LAMPs) and sialyl Lewis antigen (Woynarowska, B. et al. (1994) J. Biol. Chem., 269(36):22797–22803). Similarly, 3- and/or 4-F-GlcNAc treatment of human ovarian, A121, tumor cells causes conspicuous reductions in the incorporation of radiolabeled sugar precursors and in the carbohydrate composition of LAMPs (Woynarowska, B. et al. (1996) Glycoconjugate J., 13(4):663–674). Preventing the glycosylation of CEA and LAMPs inhibits their capacity to function as homotypic and heterotypic adhesion molecules, respectively, and, therefore, reduces human colon and ovarian tumor cell adhesion and metastatic potential, in vivo (Woynarowska, B. et al. (1994) J. Biol. Chem., 269(36):22797–22803; Dimitroff, C. J. (1999) Thesis dissertation. SUNY (Buffalo Roswell Park Graduate School)).